The goal of this proposal is to identify, isolate, and characterize both immunologically and structurally the surface-exposed portions of the major outer membrane (OM) protein (P.1) of Neisseria gonorrhoeae (GC). There is strong evidence to indicate that the surface-exposed portions of P.1s carry both unique and commom immunodeterminant sites which react with immunoglobin. In addition, it seems logical that such regions might mediate host-parasite interactions. By the techniques of 125I-labeled peptide mapping, surface-peptide mapping, and high-performance liquid chromatography, the surface-exposed regions of P.1s can be identified and isolated. Those surface-peptides which carry immunoreactive determinants, as assessed by their ability to bind P.1-specific monoclonal antibody, could prove to be valuable immunoprophylactic reagents (i.e., "peptide vaccines") as well as specific reagents to probe host-parasite interaction. Toward this end, those peptides which react with anti-P.1 antibody will be used to elicit both monoclonal and polyclonal antibody. This anti-P.1 peptide antibody will then be used in experiments to establish its ability to bind with both homologous and heterologous P.1s in intact GC and to establish its ability to kill GC in in vitro cidal assays. Further, sequencing of the surface-exposed fragments will allow for the production of synthetic peptides and the production of DNA oligomes both to probe for successful incorporation of GC P.1 DNA into cloning vectors and for direct incorporation of DNA coding for surface-fragments for large scale biosynthesis. Such experiments may provide safe and effective antibacterial vaccines and specific reagents to help elucidate the role of P.1 in the immunology and pathology of N. gonorrhoeae.